So I've been dealing with this issue for a while. I can hear the individual note on and note off signals when I play my SamplerBox via midi. It's loud enough that it's a problem. My macbook is my sequencer, it has one audio/midi interface, and one midi only interface. Typically I route midi from my controller, to the audio/midi interface, into my software, then the software either sends it out the audio/midi interface to the raspberry pi, or out the midi-only interface to my 4 hardware instruments. Today I discovered that if I connect my controller directly to my SamplerBox, I can play notes without hearing the note on/off signals. That is great, but I still have the same problem when playing back sequences from the macbook. Any suggestions? Is it the cheap interface on my raspberry pi? I can't make any sense of it...